In this exercise designed for a large lecture, students investigate differences in seed dispersal between two tropical tree species, one wind-dispersed and one bird-dispersed. This exercise was done in an introductory ecology and evolutionary biology course at the university level. In the exercise, students learn about mutualism using seed dispersal as a case study. By comparing wind dispersal of seeds with dispersal by animals, students think about how fruits evolved and the pros and cons of different plant reproductive strategies. After a brief explanation of how seed shadows are calculated in the field, students make predictions about the seed shadow of the two species and then compare their predictions to seed dispersal patterns revealed in graphs. Students also explore the relationship between seed survival as a function of distance from the maternal tree to understand why seeds need to disperse at all, and the relationship between form and function of seeds. Students are then asked to consider how different seed dispersal patterns might impact the distributions of different tree species in a community, thus forming a bridge between concepts of population ecology and community ecology. As an assessment, a Kahoot quiz was used to assess students ability to analyze and interpret seed shadow graphs. A homework assignment was given to further reinforce concepts covered in the lecture, and to extend the lesson to thinking about how habitat fragmentation might impact critical processes like seed dispersal, and what this means for management and conservation of ecosystems.
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